Method of making a magnetic head assembly having open yoke write head with highly defined narrow track width

ABSTRACT

A magnetic head assembly has an open yoke type write head constructed on top of a read head so that the write head can be constructed with a very narrow track width without restraint by the requirements of the read head. The write head has first and second pole piece portions wherein the second pole piece portion has separate front and back layer portions. A coil layer is wrapped around only the first pole piece portion and the back layer portion so that the front layer portion can be constructed separately to provide a narrow track width. Further, in a preferred embodiment the front layer portion has a reduced thickness and a higher magnetic moment than the thickness and magnetic moment of the first pole piece portion and the back layer portion. Still further, in a preferred embodiment the first pole piece portion and the back layer portion are planar due to planarization of underlying layers.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a magnetic head assembly havingan open yoke write head with a highly defined narrow track width and,more particularly, to a magnetic head assembly which includes the highlydefined write head configured above a read head.

[0003] 2. Description of the Related Art

[0004] The heart of a computer is an assembly that is referred to as amagnetic disk drive. The magnetic disk drive includes a rotatingmagnetic disk, write and read heads that are suspended by a suspensionarm above the rotating disk and an actuator that swings the suspensionarm to place the read and write heads over selected circular tracks onthe rotating disk. The read and write heads are directly located on aslider that has an air bearing surface (ABS). The suspension arm biasesthe slider into contact with the surface of the disk when the disk isnot rotating but, when the disk rotates, air is swirled by the rotatingdisk adjacent the ABS causing the slider to ride on an air bearing aslight distance from the surface of the rotating disk. When the sliderrides on the air bearing the write and read heads are employed forwriting magnetic impressions to and reading magnetic impressions fromthe rotating disk. The read and write heads are connected to processingcircuitry that operates according to a computer program to implement thewriting and reading functions.

[0005] A prior art write head includes a coil layer embedded in first,second and third insulation layers (insulation stack), the insulationstack being sandwiched between first and second pole piece layers. A gapis formed between the first and second pole piece layers by a gap layerat an air bearing surface (ABS) of the write head and the pole piecelayers are connected at a back gap. Current conducted to the coil layerinduces a magnetic field in the pole pieces which causes flux across thegap at the ABS for the purpose of writing the aforementioned magneticimpressions in tracks on moving media, such as in circular tracks on theaforementioned rotating disk.

[0006] In the prior art write head the second pole piece layer isdirectly above the first pole piece layer with only the aforementionedinsulation stack located therebetween. Unfortunately, when the coillayer induces magnetic flux in the first and second pole pieces there isa portion of this flux that leaks between the first and second polepieces which causes a reduction in a write signal across the gap. Thisloss is sometimes compensated for by increasing the number of turns ofthe pancake-shaped coil layer. An increase in the number of turns in thecoil layer, however, increases heat within the head. The heat can causea protrusion of an overcoat layer at the ABS due to expansion of theinsulation stack. Further, the overlying relationship of the first andsecond pole pieces results in magnetic leakage which degrades the datarate performance. This means that there are less bits of informationwritten by the write head per inch of track on the rotating disk.Accordingly, there is a strong felt need to provide a write head whichhas less leakage between the first and second pole pieces and improvedheat dissipation.

[0007] The aforementioned problems were overcome in a commonly assignedU.S. Pat. No. 5,164,869. In this patent, first and second pole piecesformed an open yoke configuration and a coil wound around the first polepiece, and then wound around the second pole piece. With thisarrangement there was less flux leakage between the first and secondpole pieces and there was better heat dissipation because of short coillength. In the patent, a flux guide structure for a read head waslocated between the first and second pole pieces. The first and secondread gap thickness along with the flux guide thickness becomes the totalthickness of the write gap. Unfortunately, the write gap of the writehead was restricted by the read head requirement. Further, since frontportions of the first and second pole pieces at the ABS served as firstand second shield layers for the flux guide, the track width of thewrite head could not be reduced below the width of the flux guide of theread head at the ABS. This restraint prevented optimizing the writehead. Accordingly, there is strong-felt need to decouple therequirements of the write head portion from the requirements of the readhead portion in order to permit the write head to have a narrow trackwidth.

SUMMARY OF THE INVENTION

[0008] The present invention is an improvement of the aforementionedcommonly assigned U.S. Pat. No. 5,164,869 which is incorporated byreference herein. In the present invention the improved write head islocated on top of the read head. Accordingly, the present write head hasan independently optimized write gap compared to the write gap taught bythe aforementioned patent. The present write head includes first andsecond pole piece portions wherein the second pole piece portion hasfront and back layer portions. The front layer portion extends from theABS, the back layer portion extends from a back gap site and the frontand back layer portions overlap and magnetically engage one another at asite that is located between the ABS and the back gap. Accordingly, thewrite coil can be constructed on the first pole piece portion and theback layer portion of the second pole piece portion, leaving the frontlayer portion for a separate construction step. This allows the frontlayer portion, which defines the second pole tip, to be constructed witha very narrow track width at the ABS. This narrow track width allowsmore tracks to be written on a rotating magnetic disk which increasesthe magnetic storage capability of a disk drive that employs the writehead. Further, the separate front layer portion of the second pole piecepermits this component to be constructed of a high magnetic momentmaterial that is higher than the magnetic moment of the material of thefirst pole piece portion and the material of the back layer portion ofthe second pole piece portion. This, in turn, permits the thickness ofthe front layer portion to be reduced which, in turn, permitsconstruction of a still more narrow track width. The present inventionalso enables the first pole piece portion and the back layer portion ofthe second pole piece portion to be planarized.

[0009] An object of the present invention is to provide an open yokewrite head which can be constructed with a narrow track width withoutimpacting performance of an accompanying read head.

[0010] Another object is to provide an open yoke write head wherein asecond pole tip portion has a narrow track width and a high magneticmoment.

[0011] Other objects and advantages of he invention will become moreapparent to those skilled in the art after considering the followingdetailed description in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a planar view of an exemplary magnetic disk drive;

[0013]FIG. 2 is an end view of a slider with a magnetic head of the diskdrive as seen in plane 2-2;

[0014]FIG. 3 is an elevation view of the magnetic disk drive whereinmultiple disks and magnetic heads are employed;

[0015]FIG. 4 is an isometric illustration of an exemplary suspensionsystem for supporting the slider and magnetic head;

[0016]FIG. 5 is an ABS view of the slider taken along plane 5-5 of FIG.2;

[0017]FIG. 6 is a partial view of the slider and a prior art magnetichead as seen in plane 6-6 of FIG. 2;

[0018]FIG. 7 is a partial ABS view of the slider taken along plane 7-7of FIG. 6 to show the read and write elements of the prior art magnetichead;

[0019]FIG. 8 is a view taken along plane 8-8 of FIG. 6 with all materialabove the write coil and write coil leads removed of the prior artmagnetic head;

[0020]FIG. 9 is a plan illustration of a first embodiment of the presentmagnetic head assembly;

[0021]FIG. 10 is a view taken along plane 10-10 of FIG. 9;

[0022]FIG. 11 is a view taken along the same plane as FIG. 10 showing amodification of the first embodiment;

[0023]FIG. 12 is a view taken along plane 12-12 of FIG. 9;

[0024]FIGS. 13A, 13B and 13C illustrate various steps in theconstruction of insulation with respect to bottom portions of the coiland the second shield layer;

[0025]FIGS. 14A, 14B and 14C illustrate another method of constructinginsulation for the bottom portions of the coil layer and the secondshield layer;

[0026]FIG. 15 is a plan illustration of a second embodiment of thepresent magnetic head assembly;

[0027]FIG. 16 is a view taken along plane 16-16 of FIG. 15;

[0028]FIG. 17 is a view taken along the same plane as FIG. 16 showing amodification of the second embodiment;

[0029]FIG. 18 is a view taken along plane 18-18 of FIG. 15;

[0030]FIG. 19 is a plan illustration of a third embodiment of thepresent magnetic head assembly; and

[0031]FIG. 20 is a view taken along plane 20-20 of FIG. 19.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Magnetic Disk Drive

[0032] Referring now to the drawings wherein like reference numeralsdesignate like or similar parts throughout the several views, FIGS. 1-3illustrate a magnetic disk drive 30. The drive 30 includes a spindle 32that supports and rotates a magnetic disk 34. The spindle 32 is rotatedby a motor 36 that is controlled by a motor controller 38. A prior artcombined read and write magnetic head 40 is mounted on a slider 42 thatis supported by a suspension 44 and actuator arm 46. A plurality ofdisks, sliders and suspensions may be employed in a large capacitydirect access storage device (DASD) as shown in FIG. 3. The suspension44 and actuator arm 46 position the slider 42 so that the magnetic head40 is in a transducing relationship with a surface of the magnetic disk34. When the disk 34 is rotated by the motor 36 the slider is supportedon a thin (typically, 0.05 to 0.01 μm) cushion of air (air bearing)between the surface of the disk 34 and the air bearing surface (ABS) 48.The magnetic head 40 may then be employed for writing information tomultiple circular tracks on the surface of the disk 34, as well as forreading information therefrom. Processing circuitry 50 exchangessignals, representing such information, with the head 40, provides motordrive signals for rotating the magnetic disk 34, and provides controlsignals for moving the slider to various tracks. In FIG. 4 the slider 42is shown mounted to a suspension 44. The components describedhereinabove may be mounted on a frame 54 of a housing 55, as shown inFIG. 3.

[0033]FIG. 5 is an ABS view of the slider 42 and the magnetic head 40.The slider has a center rail 56, which supports the magnetic head 40,and side rails 58 and 60. The rails 56, 58 and 60 extend from a crossrail 62. With respect to rotation of the magnetic disk 34, the crossrail 62 is at a leading edge 64 of the slider and the magnetic head 40is at a trailing edge 66 of the slider.

Prior Art Magnetic Head

[0034]FIG. 6 is a side cross-sectional elevation view of the prior artmagnetic head 40, which includes a write head portion 70 and a read headportion 72, the read head portion having a sensor 74. FIG. 7 is an ABSview of FIG. 6. The 74 is sandwiched between first and second gap layers76 and 78, and the gap layers are sandwiched between first and secondshield layers 80 and 82. In response to external magnetic fields, theresistance of the sensor 74 changes. A sense current I_(S) conductedthrough the sensor causes these resistance changes to be manifested aspotential changes. These potential changes are then processed asreadback signals by the processing circuitry 50 shown in FIG. 3.

[0035] The write head portion of the magnetic head includes a coil layer84 sandwiched between first and second insulation layers 86 and 88. Athird insulation layer 90 may be employed for planarizing the head toeliminate ripples in the second insulation layer caused by the coillayer 84. The first, second and third insulation layers are referred toin the art as an “insulation stack”. The coil layer 84 and the first,second and third insulation layers 86, 88 and 90 are sandwiched betweenfirst and second pole piece layers 92 and 94. The first and second polepiece layers 92 and 94 are magnetically coupled at a back gap 96 andhave first and second pole tips 98 and 100 which are separated by awrite gap layer 102 at the ABS. The first pole piece layer 92 isseparated from the second shield layer 82 by an insulation layer 103.This head is known as a piggyback head because the second shield layer82 and the first pole piece layer 92 are separate layers. In a mergedhead the second shield layer 82 and the first pole piece layer 92 are acommon layer. As shown in FIGS. 2 and 4, first and second solderconnections 104 and 106 connect leads from the sensor 74 to leads 112and 114 on the suspension 44, and third and fourth solder connections116 and 118 connect leads 120 and 122 from the coil 84 (see FIG. 8) toleads 124 and 126 on the suspension.

[0036] Unfortunately, because of the overlying relationship of the firstand second pole pieces 92 and 94, as shown in FIG. 6, flux induced intothese pole pieces by the pancake-shaped coil layer 84 leaks betweenthese pole pieces, which reduces the amount of flux fringing across thegap 102 which, in turn, reduces the strength of the write signal writteninto the rotating magnetic disk. While this deficiency may be overcomeby increasing the number of turns of the coil layer 84, this willincrease coil resistance and the amount of heat generated by the headwhich may damage sensitive components in the read sensor 74 and/or causethe insulation stack (layers 86, 88 and 90) to expand and protrude anovercoat layer at 42 forwardly of the ABS. The increased coil turns mayfurther require the first and second pole pieces 92 and 94 to have alonger length which further increases the flux leakage and reduces theefficiency of the write head. Further, the overlying relationship of thefirst and second pole pieces 92 and 94 increases magnetic inductance inthe magnetic circuit of the write head. All of these effects reduce thenumber of bits per second which can be written into the rotatingmagnetic disk. This equates to an undesirable decrease in the data rateand a reduction in the storage capability of the magnetic disk drive.The present invention overcomes these problems as well as theaforementioned problems associated with the magnetic head assemblydescribed by the aforementioned patent.

The Invention

[0037] A first embodiment 200 of the present magnetic head assembly isshown in part on a top flat surface 202 of aluminum oxide (Al₂O₃) of asubstrate 204. As shown in FIGS. 9 and 10, the read head portion of themagnetic head assembly includes a sensor 210 that is located betweenfirst and second nonmagnetic electrically insulative first and secondread gap layers 212 and 214 which, in turn, are located betweenferromagnetic first and second shield layers 216 and 218. First andsecond lead layers 220 and 222 are connected to first and second sideedges (not shown) of the sensor 210 which extend laterally and areconnected to other lead layers (not shown) that extend rearwardlyoutside of the write head portion which is to be described next.

[0038] The write head portion which is on top of the read head portionis separated from the read head portion by a nonmagnetic spacer layer230. The write head portion includes first and second pole pieceportions 232 and 234 that, when projected in a plane parallel to the topflat surface 202 of the substrate 204, extend about an opening 236 in anopen yoke configuration. Each of the first and second pole pieceportions 232 and 234 extend from the ABS to a back gap site 238. Anonmagnetic write gap layer 240 is located between the first and secondpole piece portions 232 and 234 at the ABS. A nonmagnetic electricallyconductive write coil 242 extends about one of the first and second polepiece portions 232 and 234 and thence about the other of the first andsecond pole piece portions in a helical relationship. As shown in FIG.12, the write coil 242 that winds around the first pole piece portion232 has bottom coil components 244 and top coil components 246. Thebottom coil components 244, which are located on the top surface 202 ofthe substrate 204, are separated from the first pole piece portion 232by a first insulation layer 248. The first pole piece portion 232 isseparated from the top coil components 246 by a second insulation layer250. The bottom and top coil components 244 and 246 are connected bystuds (not shown) which extend through vias (not shown) in the first andsecond insulation layers 248 and 250, which construction is well knownin the art.

[0039] Exemplary construction of the insulation layer 248 is illustratedin FIGS. 13A-13C. In FIG. 13A the bottom write coil layer components 244and the second shield layer 218 are shown constructed on the top surface202 of the substrate 204. In FIG. 13B aluminum oxide (Al₂O₃) is sputterdeposited on the substrate which results in an uneven top surface. InFIG. 13C the uneven top surface of the aluminum oxide is polished bychemical mechanical polishing (CMP) which results in a top planarsurface 252 that is parallel to the top flat surface 202 of thesubstrate. The chemical mechanical polishing shown in FIG. 13C may leavea thin insulator thickness above the top portion of the second shieldlayer 218 which may provide the necessary spacer layer. The first polepiece portion 232 may be constructed on the surface 252, as shown inFIG. 12. The second insulation layer 250, shown in FIG. 12, may be aphotoresist layer which covers the top of the first pole piece layerportion 232 and fills in on each side of the first pole piece layerportion on top of the surface 252. The photoresist layer 250 is spun onthe wafer substrate, patterned and then hard baked to form theconfiguration shown in FIG. 12.

[0040] Another exemplary method of constructing a first insulation layer248 is shown in FIGS. 14A-14C. The second shield layer 218 is formed onthe top surface 202 of the substrate 204. As shown in FIG. 14A, a lowerinsulation layer 254 is sputter deposited on the second shield layer 218and on the top surface 202 of the wafer substrate. In FIG. 14B the lowerwrite coil components 244 are constructed on the lower insulation layer254. In FIG. 14C photoresist is spun on the wafer, patterned and hardbaked to provide the first insulation layer 248. The lower insulationlayer 254 may provide the aforementioned spacer layer 230 shown in FIG.10.

[0041] As shown in FIG. 10 back edges of the first and second shieldlayers 216 and 218 may be exposed when the shield layers are patterned.Insulation behind the first and second shield layers 216 and 218 may beremoved which exposes the back edges of these layers. In order to coverthese back edges a first photoresist layer 260 may be spun on the wafer,patterned and baked to provide the configuration shown in FIG. 10. Thefirst pole piece portion 232 may extend rearwardly over the firstphotoresist layer 260 toward the back gap. A second photoresist layer262 is shown on the first pole piece portion 232 which defines a zerothroat height (ZTH) at 264. The zero throat height is the location wherethe first and second pole piece portions 232 and 234 first commence toseparate after the ABS. The write gap layer 240 is located between thefirst and second pole piece portions 232 and 234 in a pole tip region ofthe write head and may extend over the top of the ZTH definingphotoresist layer 262. This write gap layer can also be located underthe resist layer 262 and on top of the first pole piece layer 232. Thewrite gap layer 240 may remain as a full film on the write head, exceptfor vias, or may be patterned as desired.

[0042] The magnetic head assembly shown in FIGS. 9 and 10 is known inthe art as a piggyback head since the second shield layer 218 and thefirst pole piece portion 232 are separate layers. When the second shieldlayer and the first pole piece portion are a common layer the magnetichead assembly is known in the art as a merged head, which is shown inFIG. 11. FIG. 11 differs from FIG. 10 in that there is no separatesecond shield layer 218 nor is there a spacer layer 230. Accordingly, acommon layer 270 serves two functions, namely a second shield layer forthe read head portion and a first pole piece portion for the write headportion.

[0043] As shown in FIG. 9, an aspect of the present invention is thatthe second pole piece portion 234 has back and front layer portions 280and 282. The back layer portion 280 extends from the back gap site 238to a first site 284 and the front layer portion 282 extends from the ABSto a second site 286. The front and back layer portions 282 and 280magnetically engage one another between the first and second sites 284and 286 in an overlapping relationship. The front layer portion 282 hasa width at the ABS that defines the track width (TW) of the write head,which width is less than the width of the first pole piece portion 232at the ABS. Accordingly, the wider portion of the first pole pieceportion 232 at the ABS provides a planar surface for the write gap layer240 and the construction of the pole tip portion of the front layerportion 282 that defines the track width.

[0044] With a photoresist frame constructed by standard photolithographytechniques, the track width of the front layer portion 282 may be verynarrow so as to promote high density tracks per inch (TPI). Further, thefront layer portion 282 may be constructed of a high magnetic momentmaterial which is higher than the magnetic moment of the materialemployed for the construction of the first pole piece portion 232 andthe back layer portion 280 of the second pole piece portion 234. This isimportant because it allows more flux to be provided at the ABS withoutsaturating the pole tip. The high magnetic moment material of the frontlayer portion 282 enables the reduction in the thickness of the frontlayer portion 282 as compared to the first pole piece portion 232 andthe back layer portion 236 of the second pole piece portion 234. Thismay allow further reduction in the track width. Exemplary material forthe front layer portion 282 is Ni₄₅Fe₅₅ and an exemplary material forthe first pole piece portion 232 and the back layer portion 280 isNi₈₁Fe₁₉.

[0045] In a preferred embodiment the thickness of the front layerportion 282 is less than a thickness of the first layer pole pieceportion 232 and the back layer portion 280 of the second pole pieceportion 234. Further, in the preferred embodiment the magnetic moment ofthe material of the front layer portion 282 is higher than the magneticmoment of the material of the first pole piece portion 232 and the backlayer portion 280. Still further, in the preferred embodiment the firstand second pole piece portions 232 and 234 are provided with first andsecond straight segments respectively around which the coil 246 iswound. An overcoat layer such as that shown at 42 in FIG. 6 covers theentire assembly shown in FIG. 10 which will cover the top exposedcomponents of the write head.

[0046] A second embodiment 300 of the present magnetic head assembly isshown in FIGS. 15 and 16. This embodiment differs from the embodiment200 shown in FIGS. 9 and 10 in that the first shield layer 316 and thefirst and second gap layers 312 and 314 extend throughout the expanse ofthe write head for planarization purposes. Accordingly, the first shieldlayer 316 is located below the bottom layer components 344 of the writecoil layer 342 as shown in FIG. 18. The bottom layer components 344 ofthe write coil layer may be constructed directly on the first and secondread gap layers 312/314. Aluminum oxide (Al₂O₃) may then be sputterdeposited on the wafer and chemically mechanically polished (CMP) toform the first insulation layer 348, which not only covers the lowercomponent portions 344 of the write coil layer but also provides a toplayer portion 349 on top of the second shield layer 318. This planarizesthe entire expanse of the write head which enables planarization of thefirst and second pole piece portions 332 and 334.

[0047] After constructing the first insulation layer 348 the first polepiece portion 332 and the back layer portion 380 of the second polepiece portion 334 are constructed as one layer which has common top andbottom film surfaces that lie in top and bottom planes that are parallelto the top surface 302 of the substrate 304. This obviates undesirableprofiles in this layer so that the magnetic performance of the polepiece portions is improved. The ZTH defining insulation layer 362 isthen constructed on top of the first pole piece portion 332 for definingthe zero throat height 364. The write gap layer 340 is then deposited ontop of the front pole tip portion of the first pole piece portion 332and on top of the ZTH defining insulation layer 362. This write gap mayalso be deposited on the bottom of the resist layer 362. It may bepatterned as desired to remove any portion of the write gap layer exceptfor that portion between the first and second pole piece portion 332 and334 at the ABS. The front layer portion 382 of the second pole pieceportion 334 is then formed so as to overlap and magnetically engage theback layer portion 380 and form the track width of the write head asdiscussed hereinabove. As in the first embodiment the front layerportion 382 may have a reduced thickness and a higher magnetic momentthan the thickness and magnetic moment of the first pole piece portion332 and the back layer portion 380.

[0048] The configuration of a magnetic head assembly shown in FIG. 16 isa piggyback type head as discussed hereinabove. The magnetic headassembly shown in FIG. 17 is a merged magnetic head and, as discussedhereinabove, is the same as FIG. 16 except a common layer 370 provides asecond shield for the read head portion and a first pole piece portionfor the write head. The first pole piece portion 332 and the back layercomponent 380 of the second pole piece portion 334 can be planarized ontop of the first and second read gap layers 312 and 314 which extendthroughout the expanse of the write head.

[0049] A third embodiment 400 of the present magnetic head assembly isshown in FIGS. 19 and 20. This embodiment differs from the previousembodiment in that the first and second pole piece portions 432 and 434are curved and the write coil 442 extends about these curved portions.FIG. 20 shows studs 490 and 492 which join the bottom and top components444 and 446. The other reference numerals in FIGS. 19 and 20 thatcorrespond to the same reference numerals in FIGS. 15-18, except thatthey are increased by 100, refer to similar components as thosedescribed for the second embodiment 300.

[0050] Clearly, other embodiments and modifications of this inventionwill occur readily to those of ordinary skill in the art in view ofthese teachings. Therefore, this invention is to be limited only by thefollowing claims, which include all such embodiments and modificationswhen viewed in conjunction with the above specification and accompanyingdrawings.

We claim:
 1. A magnetic head assembly located on a flat film surface ofa substrate and having a read head and a write head that form a portionof an air bearing surface (ABS) at a forward end of the assemblycomprising: the write head having a track width at the ABS andincluding: ferromagnetic first and second pole piece portions that, whenprojected in a plane parallel to said film surface of the substrate,extend about an opening; each of the first and second pole pieceportions extending from the ABS to a back gap site; a nonmagnetic writegap layer located between the first and second pole piece portions atthe ABS; a nonmagnetic electrically conductive write coil extendingabout one of the first and second pole piece portions and thence aboutthe other of the first and second pole piece portions; the read headincluding: a read sensor and first and second nonmagnetic electricallyinsulative read gap layers; the read sensor being located between thefirst and second read gap layers; a ferromagnetic first shield layer;and the first and second gap layers being located between the firstshield layer and the first pole piece portion of the write head.
 2. Amagnetic head assembly as claimed in claim 1 wherein the write headfurther includes: the second pole piece portion having front and backlayer portions, the back layer portion extending from the back gap siteto a first site that is located between the ABS and the write coil aboutthe second pole piece portion and the front portion extending from theABS to a second site that is located between the ABS and said write coilabout the second pole piece portion so that the first site is locatedbetween the ABS and said second site and the second site is locatedbetween the first site and said back gap site; the front and back layerportions of the second pole piece portion magnetically engaging oneanother between said first and second sites; and the front layer portionof the second pole piece portion having a width at the ABS that definessaid track width of the write head and that is less than a width of thefirst pole piece portion at the ABS.
 3. A magnetic head assembly asclaimed in claim 2 including: the first pole piece portion having afront portion at the ABS that interfacially engages the second read gaplayer.
 4. A magnetic head assembly as claimed in claim 2 including: theread head having a ferromagnetic second shield layer; the first andsecond read gap layers being located between the first and second shieldlayers; and a nonmagnetic electrically insulative spacer layer locatedbetween the second shield layer and the first pole piece portion.
 5. Amagnetic head assembly as claimed in claim 2 including: a zero throatheight (ZTH) defining insulation layer between the first pole pieceportion and the front layer portion for commencing separation of thefront layer portion from the first pole piece portion at a ZTH locationbetween the ABS and said back gap site.
 6. A magnetic head assembly asclaimed in claim 2 including: between the ABS and the back gap site, thefirst pole piece portion and the back layer portion of the second polepiece portion having first and second straight segments respectively;and with respect to said first and second pole piece portions, saidwrite coil extending about only each of said first and second straightsegments.
 7. A magnetic head assembly as claimed in claim 6 wherein thefirst and second straight segments have a common first film surface thatlies in a plane that is parallel to said flat film surface of thesubstrate.
 8. A magnetic head assembly as claimed in claim 2 including:between the ABS and the back gap site, the first pole piece portion andthe back layer portion of the second pole piece layer portion havingfirst and second curved segments respectively; and with respect to saidfirst and second pole piece portions, said write coil extending aboutonly each of said first and second curved segments.
 9. A magnetic headassembly as claimed in claim 8 wherein the first and second curvedsegments have a common first film surface that lies in a plane that isparallel to said flat film surface of the substrate.
 10. A magnetic headassembly as claimed in claim 2 including: each of the first pole pieceportion and the back layer portion of the second pole piece portionhaving a first thickness and the front layer portion thereof having asecond thickness; and the second thickness being less than the firstthickness.
 11. A magnetic head assembly as claimed in claim 10 whereinthe front layer portion has a magnetic moment that is greater than amagnetic moment of each of the first pole piece portion and the backlayer portion.
 12. A magnetic head assembly as claimed in claim 11wherein all of the first pole piece portion and the back layer portionhave a common first film surface that lies in a plane that is parallelto said flat film surface of the substrate.
 13. A magnetic head assemblyas claimed in claim 12 including: a zero throat height (ZTH) defininginsulation layer between the first pole piece portion and the frontlayer portion of the second pole piece portion for commencing separationof the front layer portion from the first pole piece portion at a ZTHlocation between the ABS and said back gap site.
 14. A magnetic headassembly as claimed in claim 13 including: between the ABS and the backgap site, the first pole piece portion and the back layer portion of thesecond pole piece portion having first and second straight segmentsrespectively; and with respect to said first and second pole pieceportions, said write coil extending about only each of said first andsecond straight segments.
 15. A magnetic head assembly as claimed inclaim 14 including: the first pole piece portion having a front portionat the ABS that interfacially engages the second read gap layer.
 16. Amagnetic head assembly as claimed in claim 14 including: the read headhaving a ferromagnetic second shield layer; the first and second readgap layers being located between the first and second shield layers; anda nonmagnetic electrically insulative spacer layer located between thesecond shield layer and the first pole piece portion.
 17. A magnetichead assembly as claimed in claim 14 wherein the front layer portion ofthe second pole piece portion is Ni₄₅Fe₅₅ and each of the first polepiece portion and the back layer portion of the second pole pieceportion is Ni₈₀Fe₂₀.
 18. A magnetic disk drive that includes a magnetichead assembly that has an air bearing surface (ABS) at a forward end ofthe assembly and that is located on a flat surface of a substrate, themagnetic head assembly having a read head and a write head, the diskdrive comprising: the write head having a track width at the ABS andincluding: ferromagnetic first and second pole piece portions that, whenprojected in a plane parallel to said film surface of the substrate,extend about an opening; each of the first and second pole pieceportions extending from the ABS to a back gap site; a nonmagnetic writegap layer located between the first and second pole piece portions atthe ABS; a nonmagnetic electrically conductive write coil extendingabout one of the first and second pole piece portions and thence aboutthe other of the first and second pole piece portions; the read headincluding: a read sensor and first and second nonmagnetic electricallyinsulative read gap layers; the read sensor being located between thefirst and second read gap layers; a ferromagnetic first shield layer;and the first and second gap layers being located between the firstshield layer and the first pole piece portion of the write head; ahousing; a magnetic disk rotatably supported in the housing; a supportmounted in the housing for supporting the magnetic head assembly withits ABS facing the magnetic disk so that the magnetic head assembly isin a transducing relationship with the magnetic disk; means for rotatingthe magnetic disk; positioning means connected to the support for mowingthe magnetic head assembly to multiple positions with respect to saidmagnetic disk; and processing means connected to the magnetic headassembly, to the means for rotating the magnetic disk and to thepositioning means for exchanging signals with the magnetic headassembly, for controlling movement of the magnetic disk and forcontrolling the position of the magnetic head assembly.
 19. A magneticdisk drive as claimed in claim 18 wherein the write head furtherincludes: the second pole piece portion having front and back layerportions, the back layer portion extending from the back gap site to afirst site that is located between the ABS and the write coil about thesecond pole piece portion and the front portion extending from the ABSto a second site that is located between the ABS and said write coilabout the second pole piece portion so that the first site is locatedbetween the ABS and said second site and the second site is locatedbetween the first site and said back gap site; the front and back layerportions of the second pole piece portion magnetically engaging oneanother between said first and second sites; and the front layer portionof the second pole piece portion having a width at the ABS that definessaid track width of the write head and that is less than a width of thefirst pole piece portion at the ABS.
 20. A magnetic disk drive asclaimed in claim 19 including: the first pole piece portion having afront portion at the ABS that interfacially engages the second read gaplayer.
 21. A magnetic disk drive as claimed in claim 19 including: theread head having a ferromagnetic second shield layer; the first andsecond read gap layers being located between the first and second shieldlayers; and a nonmagnetic electrically insulative spacer layer locatedbetween the second shield layer and the first pole piece portion.
 22. Amagnetic disk drive as claimed in claim 19 including: each of the firstpole piece portion and the back layer portion of the second pole pieceportion having a first thickness and the front layer portion thereofhaving a second thickness; and the second thickness being less than thefirst thickness.
 23. A magnetic disk drive as claimed in claim 22wherein the front layer portion has a magnetic moment that is greaterthan a magnetic moment of each of the first pole piece portion and theback layer portion.
 24. A magnetic disk drive as claimed in claim 23wherein all of the first pole piece portion and the back layer portionof the second pole piece portion have a common first film surface thatlies in a plane that is parallel to said flat film surface of thesubstrate.
 25. A magnetic disk drive as claimed in claim 24 including: azero throat height (ZTH) defining insulation layer between the firstpole piece portion and the front layer portion for commencing separationof the front layer portion from the first pole piece portion at a ZTHlocation between the ABS and said back gap site.
 26. A magnetic diskdrive as claimed in claim 25 including: between the ABS and the back gapsite, the first pole piece portion and the back layer portion of thesecond pole piece portion having first and second straight segmentsrespectively; and with respect to said first and second pole pieceportions, said write coil extending about only each of said first andsecond straight segments.
 27. A magnetic disk drive as claimed in claim26 including: the first pole piece portion having a front portion at theABS that interfacially engages the second read gap layer.
 28. A magneticdisk drive as claimed in claim 26 including: the read head having aferromagnetic second shield layer; the first and second read gap layersbeing located between the first and second shield layers; and anonmagnetic electrically insulative spacer layer located between thesecond shield layer and the first pole piece portion.
 29. A magneticdisk drive as claimed in claim 26 wherein the front layer portion of thesecond pole piece portion is Ni₄₅Fe₅₅ and each of the first pole pieceportion and the back layer portion of the second pole piece portion isNi₈₀Fe₂₀.
 30. A method of making a magnetic head assembly on a flat filmsurface of a substrate wherein the assembly has a read head and a writehead that have a track width and that form a portion of an air bearingsurface (ABS) at a forward end of the assembly comprising in unorderedsequence: a making of the write head including: forming ferromagneticfirst and second pole piece portions that extend from the ABS to a backgap site and that, when projected in a plane parallel to said filmsurface of the substrate, extend about an opening; forming a nonmagneticwrite gap layer between the first and second pole piece portions at theABS; forming a nonmagnetic electrically conductive write coil extendingabout one of the first and second pole piece portions and thence aboutthe other of the first and second pole piece portions; a making of theread head including: forming a read sensor between first and secondnonmagnetic electrically insulative read gap layers; forming aferromagnetic first shield layer with the first and second gap layersbeing located between the first shield layer and the first pole pieceportion of the write head.
 31. A method as claimed in claim 30 whereinthe making of the write head further includes: forming the second polepiece portion with front and back layer portions with the back layerportion extending from the back gap site to a first site that is locatedbetween the ABS and the write coil about the second pole piece portionand with the front layer portion extending from the ABS to a second sitethat is located between the ABS and said write coil about the secondpole piece portion so that the first site is located between the ABS andsaid second site and the second site is located between the first siteand said back gap site; magnetically engaging the front and back layerportions of the second pole piece portion with one another between saidfirst and second sites; and forming the front layer portion of thesecond pole piece portion with a width at the ABS that defines saidtrack width of the write head and that is less than a width of the firstpole piece portion at the ABS.
 32. A method as claimed in claim 31including: forming the first pole piece portion with a front portion atthe ABS that interfacially engages the second read gap layer.
 33. Amethod as claimed in claim 31 including: forming the read head with aferromagnetic second shield layer; the first and second read gap layersbeing formed between the first and second shield layers; and forming anonmagnetic electrically insulative spacer layer located between thesecond shield layer and the first pole piece portion.
 34. A method asclaimed in claim 31 including: forming a zero throat height (ZTH)defining insulation layer between the first pole piece portion and thefront layer portion for commencing separation of the front layer portionfrom the first pole piece portion at a ZTH location between the ABS andsaid back gap site.
 35. A method as claimed in claim 31 including:between the ABS and the back gap site, forming the first pole pieceportion and the back layer portion of the second pole piece portion withfirst and second straight segments respectively; and with respect tosaid first and second pole piece portions, extending said write coilabout only each of said first and second straight segments.
 36. A methodas claimed in claim 35 wherein the first and second straight segmentsare formed with a common first film surface that lies in a plane that isparallel to said flat film surface of the substrate.
 37. A method asclaimed in claim 31 including: between the ABS and the back gap site,forming the first pole piece portion and the back layer portion of thesecond pole piece layer portion with first and second curved segmentsrespectively; and with respect to said first and second pole pieceportions, extending the write coil about only each of said first andsecond curved segments.
 38. A method as claimed in claim 37 wherein thefirst and second curved segments are formed with a common first filmsurface that lies in a plane that is parallel to said flat film surfaceof the substrate.
 39. A method as claimed in claim 31 including: formingeach of the first pole piece portion and the back layer portion with afirst thickness and forming the front layer portion with a secondthickness wherein the second thickness is less than the first thickness.40. A method as claimed in claim 39 forming the front layer portion witha magnetic moment that is greater than a magnetic moment of each of thefirst pole piece portion and the back layer portion.
 41. A method asclaimed in claim 40 wherein all of the first pole piece portion and theback layer portion are formed with a common first film surface that liesin a plane that is parallel to said flat film surface of the substrate.42. A method as claimed in claim 41 including: forming a zero throatheight (ZTH) defining insulation layer between the first pole pieceportion and the front layer portion for commencing separation of thefront layer portion from the first pole piece portion at a ZTH locationbetween the ABS and said back gap site.
 43. A method as claimed in claim42 including: between the ABS and the back gap site, forming the firstpole piece portion and the back layer portion of the second pole pieceportion with first and second straight segments respectively; and withrespect to said first and second pole piece portions, extending saidwrite coil about only each of said first and second straight segments.44. A method as claimed in claim 43 including: forming the first polepiece portion with a front portion at the ABS that interfacially engagesthe second read gap layer.
 45. A method as claimed in claim 43including: forming the read head with a ferromagnetic second shieldlayer; the first and second read gap layers being formed between thefirst and second shield layers; and forming a nonmagnetic electricallyinsulative spacer layer located between the second shield layer and thefirst pole piece portion.
 46. A method as claimed in claim 43 whereinthe front layer portion is formed of Ni₄₅Fe₅₅ and each of the first polepiece portion and the back layer portion is formed of Ni₈₀Fe₂₀.